PROJECT SUMMARY/ABSTRACT Research has suggested that there is an increased risk of cancer associated with long-term exposure to drinking water containing halogenated disinfection by-products (DBPs). Trihalomethanes (THMs) are the most common class of halogenated DBPs formed during water chlorination. Every year, thousands of drinking water treatment plants (WTPs) struggle with THMs compliance issues often allocating significant portions of the operating budget towards electrical and chemical means to minimize THMs formation. Unfortunately, most WTP operators adjust treatment processes without having on-site, real-time THMs concentration data to base their decisions on, leading to excess chemical and energy usage and higher operating costs. Standard methods are suitable for quarterly compliance monitoring THMs, but are often too expensive and not well-suited for continuous real-time monitoring. While there are commercial devices for on-site, real-time THMs monitoring they are not affordable to most WTPs. We propose to develop a commercial version of our pre-prototype TotalTHM-NOW analyzer at a price point of ~$25K to provide most WTPs the ability to respond in real-time to minimize THMs concentrations produced at the WTP and in the distribution system. This lowers the risk of cancer from THMs for communities across the Unites States, large and small, rural and metro. The TotalTHM-NOW analyzer is fully automated and is designed for operators with skill levels consistent with typical WTP personnel. Ultimately, the result of this SBIR proposal will be to determine the technical feasibility of reducing costs and establish that the TotalTHM- NOW analyzer provides reliable THMs concentration data in side-by side comparison studies with our established THM-RR system.